The state of the art literature is filled up with a variety of container closures. As far as multi layer closures are concerned, there are basically at least two main types, one where the end closure is penetrated in two steps, implying that the outer layer is first removed by a grip device and a tearing denotation, whereafter the inner layer is punctured, normally with any type of pointed object, and a second type where the outer layer and inner layer are removed in unison or simultaneously. Frequently, the former type of cover is identified as a two step cover and the latter one as a one step cover.
The technique of using a weld joint, adhesive joint or other connecting means at both sides of a tearing denotation, generally with a minor extension crosswise the tearing denotation is well established and a number of different techniques have been developed for providing and controlling the strength relations between the inner layer and the weld joint along the tearing denotations.
As mentioned at the introduction, splash sometimes will make it more difficult to handle the said one step end closures, resulting in an uncontrollable splashing and contamination.